Step stool



FIG. 1 is a perspective view of a step stool showing a first embodiment of the new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a perspective view showing a second embodiment of the new design; and,

FIG. 8 is a perspective view showing a third embodiment of the new design. 

The ornamental design for a step stool, as shown and described. 